The present invention relates to a well treating process for installing a bundle of strands inclusive of at least two strands having different diameters in different locations along their lengths. More particularly, the invention relates to installing an electrical heater capable of heating a long interval of subterranean earth formation and, where desired, being arranged to facilitate logging the temperature of the heated zone through a spoolable well conduit extending from a surface location to the interval being heated.
It is known that benefits can be obtained by heating intervals of subterranean earth formations to relatively high temperatures for relatively long times. Such benefits may include the pyrolyzing of an oil shale formation, the consolidating of unconsolidated reservoir formations, the formation of large electrically conductive carbonized zones capable of operating as electrodes within reservoir formations, the thermal displacement of hydrocarbons derived from oils or tars into production locations, etc. Prior processes for accomplishing such results are contained in patents such as the following, all of which are U.S. patents. U.S. Pat. No. 2,732,195 describes heating intervals of 20 to 30 meters within subterranean oil shales to temperatures of 500.degree. to 1000.degree. C. with an electrical heater having iron or reuseable chromium alloy resistors. U.S. Pat. No. 2,781,851 by G. A. Smith describes using a mineral-insulated and copper-sheathed low resistance heater cable containing three copper conductors at temperatures up to 250.degree. C. for preventing hydrate formation, during gas production, with that heater being mechanically supported by steel bands and surrounded by an oil bath for preventing corrosion. U.S. Pat. No. 3,104,705 describes consolidating reservoir sands by heating residual hydrocarbons within them until the hydrocarbons solidify, with "any heater capable of generating sufficient heat" and indicates that an unspecified type of an electrical heater was operated for 25 hours at 1570.degree. F. U.S. Pat. No. 3,131,763 describes an electrical heater for initiating an underground combustion reaction within a reservoir and describes a heater with resistance wire helixes threaded through insulators and arranged for heating fluids, such as air, being injected into a reservoir. U.S. Pat. No. 4,415,034 describes a process for forming a coked-zone electrode in an oil-containing reservoir formation by heating fluids in an uncased borehole at a temperature of up to 1500.degree. F. for as long as 12 months.